This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Lanthanum carbonate (LaCO3) is an oral phosphate binder widely used in end-stage renal disease (ESRD). Preclinical animal studies reported the highest La concentrations outside the gut to be in mesenteric lymph nodes. We observed previously unreported La deposition visible by light microscopy and confirmed by scanning electron microscopy with energy dispersive x-ray spectroscopy in a mesenteric lymph node at autopsy following LaCO3 administration. Although LaCO3 is generally thought to be minimally absorbed, this demonstration suggests the need for further investigation of the extent and potential effects of such absorption. To this end samples will be measured using the microprobe to examine the extent of La distribution and the chemical forms of various deposits.